Line Segment in LaTeX (\overline{AB})

Where it is used

Bar over AB, the standard notation for the line segment between points A and B.

Geometry texts write \overline{AB} for the segment and plain AB for its length, so \overline{AB} \cong \overline{CD} pairs with AB = CD. The bar stretches over the whole argument, unlike \bar{x}, which is a fixed-width accent for a single letter. Other meanings of \overline include the complex conjugate \overline{z}, the closure of a set \overline{A}, and negation in Boolean algebra, \overline{A \cdot B}. Rays and lines use \overrightarrow{AB} and \overleftrightarrow{AB}, which mark direction or infinite extent.

Minimal compilable example

Paste this into an empty .tex file and compile it with pdfLaTeX, XeLaTeX or LuaLaTeX.

\documentclass{article}
\begin{document}
Line Segment: $\overline{AB}$

\[ \overline{AB} \cong \overline{CD} \]
\end{document}

Related symbols

• Wide Vector\overrightarrow{AB}
• Perpendicular\perp
• Line Arrow (over AB)\overleftrightarrow{AB}
• Double Prime (inches/seconds)''
• Pi\pi
• Prime (feet/minutes)'

Frequently asked questions

How do I write Line Segment in LaTeX?

Type \overline{AB} in math mode, for example $\overline{AB} \cong \overline{CD}$. It works in plain LaTeX without loading any package.

Which package do I need for \overline{AB}?

None. \overline{AB} is part of standard LaTeX, so it compiles with nothing in the preamble but the document class.

Can I use \overline{AB} in text mode, or only in math mode?

Only in math mode. Outside $...$ LaTeX stops with "Missing $ inserted", so write $\overline{AB}$ in running text.